1. Field of the Invention
The present invention relates to a data processor for a wavemeter which executes data processing to display optical frequencies/wavelengths of optical signals measured by the wavemeter and to a data processing method for the wavemeter.
2. Description of the Related Art
In recent years, a sudden increase in data communication demands has requested higher-capacity optical communications. In order to meet this request, the Wavelength Division Multiplexing (WDM) transmission technology has come into service and has been upgraded actively. Higher-performance wavemeters are in need in order to evaluate transmission systems and optical devices utilizing the WDM transmission technology.
In a conventional wavemeter used for evaluating transmission systems and optical devices utilizing the WDM transmission technology, a series of processing described below used to be repeated sequentially: digital interference signal data obtained via A/D sampling of interference signals input from an interferometer is temporarily stored in buffer; the digital interference data stored in the buffer is read by the Digital Signal Processor (DSP) to convert the data to frequency data; and the frequency data is further converted to optical frequency data or optical wavelength data.
Conventional wavemeters use, for example, a clock generator 31 and a trigger circuit 32 shown in FIG. 3 as an external circuit for setting the sampling start timing for an A/D sampler. In the circuit configuration shown in FIG. 3, the clock generator 31 outputs sample start signals to the A/D sampler depending on trigger signals output from the trigger circuit 32.
In the circuit configuration shown in FIG. 3, the timing at which sample start signals are output is constant and in the A/D sampler, the fixed timing for starting sampling of interference signals is set via the input timing of the sample start signals.
However, in a conventional wavemeter used for evaluating transmission systems and optical devices utilizing the WDM transmission technology, sampling start signals output from the circuit shown in FIG. 3 were used to set the fixed timing for starting sampling of interference signals, thus presenting the following problems.
For example, in case that the rise timing of effective signal components contained in interference signals has changed due to individual difference or secular change of the A/D sampler, or optical signals to be measured, necessary adjustment of the sampling start timing is impossible via the circuit configuration in FIG. 3. This has degraded operability and reliability of the wavemeter.
An object of the invention is to provide a data processor for a wavemeter equipped with an adjustment mechanism for enabling arbitrary adjustment of the sampling start timing for an A/D sampler depending on the individual difference or secular change of the A/D sampler, or optical signals to be measured, and a data processing method for the wavemeter.
According to an aspect of the invention, there is provided a data processor for a wavemeter which processes interference signals of the optical signals in order to display optical frequencies/wavelengths of optical signals measured by the wavemeter, characterized in that the data processor comprises:
data conversion means for sampling and converting the interference signals to digital interference signal data (for example, an A/D sampler 3 in FIG. 1),
start timing setting means for setting the sampling start timing for the data conversion means (for example, a trigger circuit 21 and a clock generator 23 in FIG. 2), and
start timing adjusting means for arbitrarily adjusting the sampling start timing set via the start timing adjusting means (for example, a delay circuit 22 in FIG. 2).
According to the aspect of the invention, in a data processor for a wavemeter which executes data processing to display optical frequencies/wavelengths of optical signals measured by the wavemeter, the data conversion means samples and converts the interference signals to digital interference signal data, the start timing setting means sets the sampling start timing for the data conversion means, and the start timing adjusting means arbitrarily adjusts the sampling start timing set via the start timing setting means.
According to another aspect of the invention is a data processing method for a wavemeter which processes interference signals of the optical signals in order to display optical frequencies/wavelengths of optical signals measured by the wavemeter, characterized in that the data processing method comprises:
a data conversion step for sampling and converting the interference signals to digital interference signal data,
a start timing setting step for setting the sampling start timing for the data conversion step, and
a start timing step for arbitrarily adjusting the sampling start timing set via the start timing step.
According to the another aspect of the invention, a data processing method for a wavemeter which executes data processing to display optical frequencies/wavelengths of optical signals measured by the wavemeter comprises
a data conversion step for sampling and converting the interference signals to digital interference signal data,
a start timing setting step for setting the sampling start timing for the data conversion step, and
a start timing step for arbitrarily adjusting the sampling start timing set via the start timing step.
Thus, in case that the rise timing of effective signal components contained in interference signals has changed depending on optical signals to be measured, adjustment of the sampling start timing can be made with ease, thus improving operability and reliability of the wavemeter.
In this case, according to the invention, a data processor for a wavemeter according to the first aspect of the invention can be such that the start timing adjusting means comprises adjustment processing means (for example, CPU 24 of FIG. 2) for executing adjustment processing to adjust the sampling start timing set via the start timing means, based on timing adjustment data input from input means.
According to the invention, the start timing adjusting means executes adjustment processing to adjust the sampling start timing set via the start timing means, based on timing adjustment data input from the input means.
In this case, same as the fourth aspect of the invention, a data processing method for a wavemeter according to the third aspect of the invention can be such that the start timing adjusting step comprises an adjustment processing step for executing processing to adjust the sampling start timing set via the start timing step, based on timing adjustment data input from input means.
According to the invention, the start timing adjusting step comprises an adjustment processing step to adjust the sampling start timing set via the start timing step, based on timing adjustment data input from the input means.
Thus, requirements for setting the sampling start timing can be changed with ease by changing adjustment processing and the sampling start timing adjustment feature can be changed with ease depending on optical signals to be measured.